FIG. 1 schematically illustrates the structure of a conventional image capturing unit. As shown in FIG. 1, the image capturing unit 1 comprises an optical lens group 11, an image sensor 12 and a casing 13. The optical lens group 11 comprises at least one lens for collecting the light beams from one object to pass through. After the light beam passing through the optical lens group 11 is sensed by the image sensor 12, the light beam is converted into an image pattern (signal) by the image sensor 12. According to the imaging signal, a corresponding image is shown on a display device. The optical lens group 11 and the image sensor 12 are accommodated within the casing 13 and securely and firmly positioned in the casing (housing) 13. Consequently, the optical lens group 11 and the image sensor 12 can be normally operated. In FIG. 1, the individual image capturing unit 1 is shown. However, since the current optical technology is constantly developed, the image capturing unit 1 can be minimized and installed in a portable electronic communication product.
Moreover, the image capturing unit 1 of FIG. 1 is only able to capture a single image in each capturing process. Nevertheless, when the demand is to have multiple images simultaneously, a direct approach is to have multiple units which may be too cumbersome. For solving this drawbacks, plural image capturing units 1 are combined together in order to capture plural images at the same time.
FIG. 2 schematically illustrates the structure of a conventional array-type image capturing apparatus. As shown in FIG. 2, the array-type image capturing apparatus 2 comprises a frame 21 and plural image capturing units 1. The plural image capturing units 1 are in an array arrangement and in a rectangular distribution through the frame 21. Moreover, the image signals corresponding to the images acquired by the plural image capturing units 1 are transmitted to a back-end processor (not shown). After the image signals are integrated and processed by the back-end processor, the integrated image is shown on a display device.
Generally, the array-type image capturing apparatus 2 is able to capture plural images in each capturing process. However, the optical functions provided by the plural image capturing units 1 are identical. For example, the optical axes of the plural image capturing units 1 are along the same direction. That is, there is no inclined angle between any two optical axes. Alternatively, all image capturing units 1 have the same field of view (FOV) or the same effective focal length (efl).
Due to the limitations of the fabricating process of the current array-type image capturing apparatus 2, the imaging quality of the image capturing unit 1 is usually insufficient. For example, the image capturing unit 1 usually has a resolution of 1M˜2M pixels only. Under this circumstance, the function provided by the array-type image capturing apparatus 2 is limited. Moreover, since the array arrangement of the array-type image capturing apparatus 2 is complicated and plural image capturing units 1 are contained in the array-type image capturing apparatus 2, the applications thereof are restricted because of the high cost. The development of current array type image capturing apparatus are also achieved by wafer-level optics and hence, the lenses are with the same principal planes and hence the same effective focal length and this actually become a restriction on the lens design. It is actually not easy to keep all array elements to have exactly the same effective focal length practically in fabrication/production.
FIG. 3 schematically illustrates the structure of another conventional image capturing apparatus. As shown in FIG. 3, the image capturing apparatus 9 comprises plural lens modules 91 and a casing 92. The lens modules 91 are fixed by the casing 92. Each lens module 91 comprises an optical lens group 911 and an optical sensor (not shown). Moreover, the image signals corresponding to the images acquired by the plural lens modules 91 are transmitted to a processor (not shown). The processor may be built in the casing 92. After the image signals are integrated and processed by the processor, a three-dimensional image is produced or shown on a display device. Likewise, the image capturing apparatus 9 is able to capture plural images in each capturing process. However, since plural optical sensors are installed within the casing 92, the volume reduction of the image capturing apparatus 9 is not obvious.
Regardless of whether the image capturing apparatus comprises a single image capturing unit or plural image capturing units, the aperture is reduced when the imaging quality of the image capturing apparatus is taken into consideration. The reduction of the aperture can increase the sharpness of the image that is acquired by the image capturing apparatus. However, if the aperture is too small, the luminance for the image capturing apparatus is insufficient. Under this circumstance, the overall performance of the image capturing apparatus is deteriorated. The aperture is related to the concept of f-number. It means that it is always difficult to have small F/# (f-number) for image-taking device in general.
FIG. 4 schematically illustrates the structure of another conventional image capturing apparatus with a flash lamp. As shown in FIG. 4, the flash lamp 7 is an individual component. The flash lamp 7 may be independently located at the outside of the image capturing apparatus 8, or the flash lamp 7 may be combined with the image capturing apparatus 8. During the process of capturing the image, the flash lamp 7 provides luminance to the operating environment of the image capturing apparatus 8. Consequently, the imaging quality is enhanced. However, since the flash lamp 7 occupies a lot of space, the use of the flash lamp 7 cannot effectively reduce the overall volume of the image capturing apparatus 8.
Therefore, while both of the overall volume and the fabricating cost are taken into consideration, it is an important issue to allow the image capturing apparatus to capture plural images in each capturing process and allow the image capturing apparatus to flexibly provide different optical functions to achieve required optical efficacy according to the practical requirements and acquire required luminance for capturing images in various situations (e.g., the situation that the aperture is reduced).